Yet, we still have pockets of upgrade resistance from calcified recesses of the web industry. Some people don’t trust computers or payback calculations. Yet it is clear that stop-to controls are far better. Just like range-finding sensors on automobiles to set (speed varying) following distance. The controls can smooth speed variations and do so more safely than you can. Still, it is disconcerting to set the cruise control (with following distance controls) at 65 mph in stop and go city traffic for someone who has been doing manual speed control for much more than a half-century now. Maybe I am the one who is calcified.
Web201.40b Length – Stop To
***201.40b – Length: Stop To
04 Slides Duration 02.36 v 15.03.09
201.40b.01 – Title Slide
Welcome to Web-Handling. My name is Dave Roisum. In this second clip in a series on length we discuss automatic stop-to controls used on winders and unwinds.
201.40b.02 – Auto Stop To What, Why
There are many reasons to be able to stop to wound roll diameter, unwind diameter or roll length. These reasons were covered in the two-day winding section of Web101. Also covered there were the sensor techniques to obtain accurate length and diameter measurements. In the paper industry, the stop-to controls are often so accurate that winder operators complain if they need to jog the unwinding roll a couple more revolutions to find an auto-flagged defect. Customers look for length readings accurate to a few feet even though this is not possible as we saw in the last clip.
In any case, the reasons for auto stops are simple: a computer can do a better job than an operator, thus reducing waste and delay. The reasons given not to are equipment cost. Yet, these systems quickly pay back as it may be little more than a couple of pages of extra code on a modern drive and the sensors to measure diameter and length are a given. Next generation systems put barcode marks on the web so that positions, lengths, permanent deformation and waste are easily traceable during manufacturing and subsequent converting and rewinding steps.
201.40b.03 – How – Drive Calculations
Without going into details, suffice it to say that the drive computer does the calculations for the stop to functions. There are two primary methods. The first is constant deceleration that is easier but slower because it has a slow speed precision final metering step. The variable deceleration method is more sophisticated because it may need to be adaptive as it adjusts stopping rates on the fly as it slows. This is most challenging when the stop to function is for diameter and there is a web thickness change.
201.40b.04 – Questions?
Thank you so very much for watching this module in my plant practical video clips. Stay tuned for the next clip as we discuss at length, more about length.